The present invention is related to the field of integrated circuits. More specifically, the present invention is related to the formation of cobalt caps on copper interconnects.
Recently, there is increasing interest in the semiconductor industry to reduce the defects on copper interconnects and properly add a cobalt capping layer to each of the copper interconnects. One area of difficulty preventing the accomplishment of low or no defects and even deposition of a cobalt capping layer on each of the copper interconnects is the cobalt wetting problem. The cobalt wetting problem involves the difficulty of electro-less cobalt solutions evenly wetting the top surface of each of the copper interconnects. Also the wetting problem increases the amount of cobalt particles that get adhered to undesired areas on the wafer.